Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R3/00—Circuits for transducers, loudspeakers or microphones
  • H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
  • H04R3/14—Cross-over networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R3/00—Circuits for transducers, loudspeakers or microphones
  • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R5/00—Stereophonic arrangements
  • H04R5/02—Spatial or constructional arrangements of loudspeakers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R5/00—Stereophonic arrangements
  • H04R5/04—Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
  • H04S3/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
  • H04S3/008—Systems employing more than two channels, e.g. quadraphonic in which the audio signals are in digital form, i.e. employing more than two discrete digital channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
  • H04S7/30—Control circuits for electronic adaptation of the sound field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
  • H04S7/30—Control circuits for electronic adaptation of the sound field
  • H04S7/302—Electronic adaptation of stereophonic sound system to listener position or orientation
  • H04S7/303—Tracking of listener position or orientation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
  • H04R2430/03—Synergistic effects of band splitting and sub-band processing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/01—Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/05—Generation or adaptation of centre channel in multi-channel audio systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/13—Aspects of volume control, not necessarily automatic, in stereophonic sound systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
  • H04S2420/07—Synergistic effects of band splitting and sub-band processing

Definitions

• Embodiments of the present disclosure generally relate to the field of audio signal processing and, more particularly, to crosstalk processing of spatially enhanced multi- channel audio.
• Stereophonic sound reproduction involves encoding and reproducing signals containing spatial properties of a sound field.
• Stereophonic sound enables a listener to perceive a spatial sense in the sound field from a stereo signal using headphones or loudspeakers.
• processing of the stereophonic sound by combining the original signal with delayed and possibly inverted or phase-altered versions of the original can produce audible and often perceptually unpleasant comb-filtering artifacts in the resulting signal.
• the perceived effects of such artifacts can range from mild coloration to significant attenuation or amplification of particular sonic elements within a mix (i.e. voice receding, etc.).
• Embodiments relate to enhancing an audio signal including a left input channel and a right input channel.
• a nonspatial component and a spatial component are generated from the left input channel and the right input channel.
• a mid compensation channel is generated by applying first filters to the nonspatial component that compensate for spectral defects from crosstalk processing of the audio signal.
• a side compensation channel is generated by applying second filters to the spatial component that compensate for spectral defects from the crosstalk processing of the audio signal.
• a left compensation channel and a right compensation channel are generated from the mid compensation channel and the side compensation channel.
• a left output channel is generated using the left compensation channel, and a right output channel is generated using the right compensation channel.
• crosstalk processing and subband spatial processing are performed on the audio signal.
• the crosstalk processing may include a crosstalk
• Crosstalk simulation may be used to generate output to head-mounted speakers to simulate crosstalk that may be experienced using loudspeakers.
• Crosstalk cancellation may be used to generate output to loudspeakers to remove crosstalk that may be experienced using the loudspeakers.
• the crosstalk processing may be performed prior to, subsequent to, or in parallel with the crosstalk cancellation.
• the subband spatial processing includes applying gains to the subbands of a nonspatial component and a spatial component of the left and right input channels. The crosstalk processing compensates for spectral defects caused by the crosstalk cancellation or crosstalk simulation, with or without the subband spatial processing.
• a system enhances an audio signal having a left input channel and a right input channel.
• the system includes circuitry configured to: generate a nonspatial component and a spatial component from the left input channel and the right input channel, generate a mid compensation channel by applying first filters to the nonspatial component that compensate for spectral defects from crosstalk processing of the audio signal, and generate a side compensation channel by applying second filters to the spatial component that compensate for spectral defects from the crosstalk processing of the audio signal.
• the circuitry is further configured to generate a left compensation channel and a right
• compensation channel from the mid compensation channel and the side compensation channel, and generates a left output channel using the left compensation channel; and generate a right output channel using the right compensation channel.
• the crosstalk compensation is integrated with subband spatial processing.
• the left input channel and the right input channel are processed into a spatial component and a nonspatial component.
• First subband gains are applied to subbands of the spatial component to generate an enhanced spatial component
• second subband gains are applied to subbands of the nonspatial component to generate an enhanced nonspatial component.
• a mid enhanced compensation channel is generated by applying filters to the enhanced nonspatial component.
• the mid enhanced compensation channel includes the enhanced nonspatial component having compensation for spectral defects from crosstalk processing of the audio signal.
• a left enhanced compensation channel and a right enhanced compensation channel are generated from the mid enhanced compensation channel.
• a left output channel is generated from the left compensation channel
• a right output channel is generated from the right enhanced compensation channel.
• a side enhanced compensation channel is generated by applying second filters to the enhanced spatial component, the side enhanced compensation channel including the enhanced spatial component having compensation for spectral defects from the crosstalk processing of the audio signal.
• the left enhanced compensation channel and the right enhanced compensation channel are generated from the mid enhanced compensation channel and the side enhanced compensation channel.
• FIG. 1 A illustrates an example of a stereo audio reproduction system for loudspeakers, according to one embodiment.
• FIG. 1B illustrates an example of a stereo audio reproduction system for headphones, according to one embodiment.
• FIG. 2A illustrates an example of an audio system for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 2B illustrates an example of an audio system for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 3 illustrates an example of an audio system for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 4 illustrates an example of an audio system for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 5 A illustrates an example of an audio system for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 5B illustrates an example of an audio system for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 5C illustrates an example of an audio system for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 6 illustrates an example of an audio system for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 7 illustrates an example of an audio system for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• FIG. 8 illustrates an example of a crosstalk compensation processor, according to one embodiment.
• FIG. 9 illustrates an example of a crosstalk compensation processor, according to one embodiment.
• FIG. 10 illustrates an example of a crosstalk compensation processor, according to one embodiment.
• FIG. 11 illustrates an example of a crosstalk compensation processor, according to one embodiment.
• FIG. 12 illustrates an example of a spatial frequency band divider, according to one embodiment.
• FIG. 13 illustrates an example of a spatial frequency band processor, according to one embodiment.
• FIG. 14 illustrates an example of a spatial frequency band combiner, according to one embodiment.
• FIG. 15 illustrates a crosstalk cancellation processor, according to one embodiment.
• FIG. 16A illustrates a crosstalk simulation processor, according to one embodiment.
• FIG. 16B illustrates a crosstalk simulation processor, according to one embodiment.
• FIGS. 17 illustrates a combiner, according to one embodiment.
• FIGS. 18 illustrates a combiner, according to one embodiment.
• FIGS. 19 illustrates a combiner, according to one embodiment.
• FIGS. 20 illustrates a combiner, according to one embodiment.
• FIGS. 21-26 illustrate plots of spatial and nonspatial components of a signal using crosstalk cancellation and crosstalk compensation, according to one embodiment.
• FIGS. 27 A and 27B illustrate tables of filter settings for a crosstalk compensation processor as a function of crosstalk cancellation delays, according to one embodiment.
• FIGS. 28 A, 28B, 28C, 28D, and 28E illustrate examples of crosstalk cancellation, crosstalk compensation, and subband spatial processing, according to some embodiments.
• FIGS. 29 A, 29B, 29C, 29D, 29E, 29F, 29G, and 29H illustrate examples of crosstalk simulation, crosstalk compensation, and subband spatial processing, according to some embodiments.
• FIG. 30 is a schematic block diagram of a computer, in accordance with some embodiments.
• the audio systems discussed herein provide crosstalk processing for spatially enhanced audio signals.
• the crosstalk processing may include crosstalk cancellation for loudspeakers, or crosstalk simulation for headphones.
• An audio system that performs crosstalk processing for spatially enhanced signals may include a crosstalk compensation processor that adjusts for spectral defects resulting from the crosstalk processing of audio signals, with or without spatial enhancement.
• a signal component (e.g., 118L, 118R) output by a speaker on the same side of the listener's head and received by the listener's ear on that side is herein referred to as“an ipsilateral sound component” (e.g., left channel signal component received at left ear, and right channel signal component received at right ear) and a signal component (e.g.,
• a contralateral sound component e.g., left channel signal component received at right ear, and right channel signal component received at left ear.
• Contralateral sound components contribute to crosstalk interference, which results in diminished perception of spatiality.
• a crosstalk cancellation may be applied to the audio signals input to the loudspeakers 110 to reduce the experience of crosstalk interference by the listener 120.
• a dedicated left speaker 130L emits sound into the left ear 125L and a dedicated right speaker 13 OR to emit sound into the right ear 125R.
• Head-mounted speakers emit sound waves close to the user’s ears, and therefore generate lower or no trans-aural sound wave propagation, and thus no contralateral components that cause crosstalk interference.
• Each ear of the listener 120 receives an ipsilateral sound component from a corresponding speaker, and no contralateral crosstalk sound component from the other speaker. Accordingly, the listener 120 will perceive a different, and typically smaller sound field with head-mounted speakers.
• a crosstalk simulation may be applied to the audio signals input to the head-mounted speakers 110 to simulate crosstalk interference as would be experienced by the listener 120 when the audio signals are output by imaginary loudspeaker sound sources 120A and 120B.
• FIGS. 2 A, 2B, 3, and 4 show examples of audio systems that perform crosstalk cancellation with a spatially enhanced audio signal E. These audio systems each receive an input signal X, and generate an output signal O for loudspeakers having reduced crosstalk interference.
• FIGS. 5A, 5B, 5C, 6, and 7 show examples of audio systems that perform crosstalk simulation with a spatially enhanced audio signal. These audio systems receive the input signal X, and generate an output signal O for head-mounted speakers that simulates crosstalk interference as would be experienced using loudspeakers.
• the crosstalk
• crosstalk processing removes spectral defects caused by the crosstalk processing of the spatially enhanced audio signal.
• the crosstalk compensation may be applied in various ways.
• crosstalk compensation is performed prior to the crosstalk processing.
• crosstalk compensation may be performed in parallel with subband spatial processing of the input audio signal X to generate a combined result, and the combined result may subsequently receive crosstalk processing.
• the crosstalk compensation is integrated with the subband spatial processing of the input audio signal, and the output of the subband spatial processing subsequently receives the crosstalk processing.
• the crosstalk compensation may be performed after crosstalk processing is performed on the spatially enhanced signal E.
• the crosstalk compensation may include enhancement (e.g., filtering) of mid components and side components of the input audio signal X.
• the crosstalk compensation enhances only the mid components, or only the side components.
• FIG. 2A illustrates an example of an audio system 200 for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 200 receives an input audio signal X including a left input channel XL and a right input channel XR.
• the input audio signal X is provided from a source component in a digital bitstream (e.g., PCM data).
• the source component may be a computer, digital audio player, optical disk player (e.g., DVD, CD, Blu-ray), digital audio streamer, or other source of digital audio signals.
• the audio system 200 generates an output audio signal O including two output channels OL and OR by processing the input channels XL and XR.
• the audio output signal O is a spatially enhanced audio signal of the input audio signal X with crosstalk compensation and crosstalk cancellation.
• the audio system 200 may further include an amplifier that amplifies the output audio signal O from the crosstalk cancellation processor 270, and provides the signal O to output devices, such as the loudspeakers 280L and 280R, that convert the output channels OL and OR into sound.
• the audio processing system 200 includes a subband spatial processor 210, a crosstalk compensation processor 220, a combiner 260, and a crosstalk cancellation processor 720.
• the audio processing system 200 performs crosstalk compensation and subband spatial processing of the input audio input channels XL, XR, combines the result of the subband spatial processing with the result of the crosstalk compensation, and then performs a crosstalk cancellation on the combined signals.
• the subband spatial processor 210 includes a spatial frequency band divider 240, a spatial frequency band processor 245, and a spatial frequency band combiner 250.
• the spatial frequency band divider 240 is coupled to the input channels XL and XR and the spatial frequency band processor 245.
• the spatial frequency band divider 240 receives the left input channel XL and the right input channel XR, and processes the input channels into a spatial (or “side”) component Y s and a nonspatial (or“mid”) component Y m .
• the spatial component Y s can be generated based on a difference between the left input channel XL and the right input channel XR.
• the nonspatial component Y m can be generated based on a sum of the left input channel XL and the right input channel XR.
• the spatial frequency band divider 240 provides the spatial component Y s and the nonspatial component Y m to the spatial frequency band processor 245. Additional details regarding the spatial frequency band divider is discussed below in connection with FIG. 12.
• the spatial frequency band processor 245 is coupled to the spatial frequency band divider 240 and the spatial frequency band combiner 250.
• the spatial frequency band processor 245 receives the spatial component Y s and the nonspatial component Y m from spatial frequency band divider 240, and enhances the received signals.
• the spatial frequency band processor 245 generates an enhanced spatial component E s from the spatial component Y s , and an enhanced nonspatial component E m from the nonspatial component Y m.
• the spatial frequency band processor 245 applies subband gains to the spatial component Y s to generate the enhanced spatial component E s , and applies subband gains to the nonspatial component Y m to generate the enhanced nonspatial component E m .
• the spatial frequency band processor 245 additionally or alternatively provides subband delays to the spatial component Y s to generate the enhanced spatial component E s , and subband delays to the nonspatial component Y m to generate the enhanced nonspatial component E m.
• the subband gains and/or delays may can be different for the different (e.g., n) subbands of the spatial component Y s and the nonspatial component Ym, or can be the same (e.g., for two or more subbands).
• the spatial frequency band processor 245 adjusts the gain and/or delays for different subbands of the spatial component Y s and the nonspatial component Y m with respect to each other to generate the enhanced spatial component E s and the enhanced nonspatial component E m.
• the spatial frequency band processor 245 then provides the enhanced spatial component E s and the enhanced nonspatial component E m to the spatial frequency band combiner 250. Additional details regarding the spatial frequency band divider is discussed below in connection with FIG. 13.
• the spatial frequency band combiner 250 is coupled to the spatial frequency band processor 245, and further coupled to the combiner 260.
• the spatial frequency band combiner 250 receives the enhanced spatial component E s and the enhanced nonspatial component E m from the spatial frequency band processor 245, and combines the enhanced spatial component E s and the enhanced nonspatial component E m into a left spatially enhanced channel EL and a right spatially enhanced channel ER.
• the left spatially enhanced channel EL can be generated based on a sum of the enhanced spatial component E s and the enhanced nonspatial component Em
• the right spatially enhanced channel ER can be generated based on a difference between the enhanced nonspatial component E m and the enhanced spatial component E s .
• the spatial frequency band combiner 250 provides the left spatially enhanced channel EL and the right spatially enhanced channel ER to the combiner 260. Additional details regarding the spatial frequency band divider is discussed below in connection with FIG. 14.
• the crosstalk compensation processor 220 performs a crosstalk compensation to compensate for spectral defects or artifacts in the crosstalk cancellation.
• the crosstalk compensation processor 240 receives the input channels XL and XR, and performs a processing to compensate for any artifacts in a subsequent crosstalk cancellation of the enhanced nonspatial component E m and the enhanced spatial component E s performed by the crosstalk cancellation processor 270.
• the crosstalk compensation processor 220 may perform an enhancement on the nonspatial component X m and the spatial component X s by applying filters to generate a crosstalk compensation signal Z, including a left crosstalk compensation channel ZL and a right crosstalk compensation channel ZR.
• the crosstalk compensation processor 220 may perform an enhancement on only the nonspatial component X m. Additional details regarding crosstalk compensation processors are discussed below in connection with FIGS. 8 through 10.
• the combiner 260 combines the left spatially enhanced channel EL with the left crosstalk compensation channel ZL to generate a left enhanced compensated channel TL, and combines the right spatially enhanced channel ER with the right crosstalk compensation channel ZR to generate a right compensation channel TR.
• the combiner 260 is coupled to the crosstalk cancellation processor 270, and provides the left enhanced compensated channel TL and the right enhanced compensation channel TR to the crosstalk cancellation processor 270. Additional details regarding the combiner 260 are discussed below in connection with FIG.
• the crosstalk cancellation processor 270 receives the left enhanced
• FIG. 2B illustrates an example of an audio system 202 for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 202 includes the subband spatial processor 210, a crosstalk compensation processor 222, a combiner 262, and the crosstalk cancellation processor 270.
• the audio system 202 is similar to the audio system 200, except that the crosstalk compensation processor 222 performs an enhancement on the nonspatial component X m by applying filters to generate a mid crosstalk compensation signal Z m .
• the combiner 262 combines the mid crosstalk compensation signal Z m with the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210. Additional details regarding the crosstalk compensation processor 222 are discussed below in connection with FIG. 10, and the additional details regarding the combiner 262 are discussed below in connection with FIG. 18.
• FIG. 3 illustrates an example of an audio system 300 for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 300 includes a subband spatial processor 310 including a crosstalk compensation processor 320, and further includes a crosstalk cancellation processor 270.
• the subband spatial processor 310 includes the spatial frequency band divider 240, the spatial frequency band processor 245, a crosstalk compensation processor 320, and the spatial frequency band combiner 250.
• the crosstalk compensation processor 320 is integrated with the subband spatial processor 310.
• the crosstalk compensation processor 320 is coupled to the spatial frequency band processor 245 to receive the enhanced nonspatial component E m and the enhanced spatial component E s , performs the crosstalk compensation using the enhanced nonspatial component E m and the enhanced spatial component E s (e.g., rather than the input signal X as discussed above for the audio systems 200 and 202) to generate a mid enhanced compensation channel Tm and a side enhanced compensation channel T s.
• the spatial frequency band combiner 250 receives the mid enhanced compensation channel Tm and a side enhanced compensation channel T s , and generates the left enhanced compensation channel TL and the right enhanced compensation channel TR.
• the crosstalk cancellation processor 270 generates output audio signal O including left output channel OL and right output channel OR by performing the crosstalk cancellation on the left enhanced compensation channel TL and the right enhanced compensation channel TR. Additional details regarding the crosstalk compensation processor 320 are discussed below in connection with FIG. 11.
• FIG. 4 illustrates an example of an audio system 400 for performing crosstalk cancellation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 400 performs crosstalk compensation after crosstalk cancellation.
• the audio system 400 includes the subband spatial processor 210 coupled to the crosstalk cancellation processor 270.
• the crosstalk cancellation processor 270 is coupled to a crosstalk compensation processor 420.
• the crosstalk cancellation processor 270 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, and performs a crosstalk cancellation to generate a left enhanced in-out-band crosstalk channel CL and a right enhanced in-out-band crosstalk channel CR.
• the crosstalk compensation processor 420 receives the left enhanced in-out- band crosstalk channel CL and a right enhanced in-out-band crosstalk channel CR, and performs a crosstalk compensation using the mid and side components of the left enhanced in-out-band crosstalk channel CL and a right enhanced in-out-band crosstalk channel CR to generate the left output channel OL and right output channel OR. Additional details regarding the crosstalk compensation processor 420 are discussed below in connection with FIGS. 8 and 9.
• FIG. 5A illustrates an example of an audio system 500 for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 500 performs crosstalk simulation for the input audio signal X to generate an output audio signal O including a left output channel OL for a left head-mounted speaker 580L and a right output channel OR for a right head-mounted speaker 580R.
• the audio system 500 includes the subband spatial processor 210, a crosstalk compensation processor 520, a crosstalk simulation processor 580, and a combiner 560.
• the crosstalk compensation processor 520 receives the input channels XL and XR, and performs a processing to compensate for artifacts in a subsequent combination of a crosstalk simulation signal W generated by the crosstalk simulation processor 580 and the enhanced channel E.
• the crosstalk compensation processor 520 generates a crosstalk compensation signal Z, including a left crosstalk compensation channel ZL and a right crosstalk compensation channel ZR.
• the crosstalk simulation processor 580 generates a left crosstalk simulation channel WL and a right crosstalk simulation channel WR.
• the subband spatial processor 210 generates the left enhanced channel EL and the right enhanced channel ER. Additional details regarding the crosstalk compensation processor 520 are discussed below in connection with FIGS. 9 and 10. Additional details regarding the crosstalk simulation processor 580 are discussed below in connection with FIGS. 16A and 16B.
• the combiner 560 receives the left enhanced channel EL, the right enhanced channel ER, the left crosstalk simulation channel WL, the right crosstalk simulation channel WR, the left crosstalk compensation channel ZL, and a right crosstalk compensation channel ZR.
• the combiner 560 generates the left output channel OL by combining the left enhanced channel EL, the right crosstalk simulation channel WR, and the left crosstalk compensation channel ZL.
• the combiner 560 generates the right output channel OR by combining the left enhanced channel EL, the right crosstalk simulation channel WR, and the left crosstalk compensation channel ZL. Additional details regarding the combiner 560 are discussed below in connection with FIG. 19.
• FIG. 5B illustrates an example of an audio system 502 for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 502 is like the audio system 500, except that the crosstalk simulation processor 580 and the crosstalk compensation processor 520 are in series.
• the crosstalk simulation processor 580 receives the input channels XL and XR and performs crosstalk simulation to generate the left crosstalk simulation channel WL and the right crosstalk simulation channel WR.
• the crosstalk compensation processor 520 receives the left crosstalk simulation channel WL and a right crosstalk simulation channel WR, and performs crosstalk compensation to generate a simulation compensation signal SC including a left simulation compensation channel SCL and a right simulation compensation channel SCR.
• the combiner 562 combines the left enhanced channel EL from the subband spatial processor 210 with the right simulation compensation channel SCR to generate the left output channel OL, and combines the right enhanced channel ER from the subband spatial processor 210 with the left simulation compensation channel SCL to generate the right output channel OR. Additional details regarding the combiner 562 are discussed below in connection with FIG. 20.
• FIG. 5C illustrates an example of an audio system 504 for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 504 is like the audio system 502, except that crosstalk compensation is applied to the input signal X prior to crosstalk simulation.
• the crosstalk compensation processor 520 receives the input channels XL and XR and performs crosstalk compensation to generate the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR.
• the crosstalk simulation processor 580 receives the left crosstalk compensation channel ZL and a right crosstalk compensation channel ZR, and performs crosstalk simulation to generate the simulation compensation signal SC including the left simulation compensation channel SCL and the right simulation compensation channel SCR.
• the combiner 562 combines the left enhanced channel EL with the right simulation compensation channel SCR to generate the left output channel OL, and combines the right enhanced channel ER with the left simulation compensation channel SCL to generate the right output channel OR.
• FIG. 6 illustrates an example of an audio system 600 for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• the crosstalk compensation processor 620 is integrated with a subband spatial processor 610.
• the audio system 600 includes the subband spatial processor 610 including a crosstalk compensation processor 620, and a crosstalk simulation processor 580, and the combiner 562.
• the crosstalk compensation processor 620 is coupled to the spatial frequency band processor 245 to receive the enhanced nonspatial component E m and the enhanced spatial component E s , performs the crosstalk compensation to generate the mid enhanced compensation channel T m and the side enhanced compensation channel T s.
• the spatial frequency band combiner 562 receives the mid enhanced compensation channel T m and a side enhanced compensation channel T s , and generates the left enhanced
• the combiner 562 generates the left output channel OL by combining the left enhanced compensation channel TL with the right crosstalk simulation channel WR, and generates the right output channel OR by combining the right enhanced compensation channel TR with the left crosstalk simulation channel WL. Additional details regarding the crosstalk compensation processor 620 are discussed below in connection with FIG. 11.
• FIG. 7 illustrates an example of an audio system 700 for performing crosstalk simulation with a spatially enhanced audio signal, according to one embodiment.
• the audio system 700 performs crosstalk compensation after crosstalk simulation.
• the audio system 700 includes the subband spatial processor 210, the crosstalk simulation processor 580, the combiner 562, and a crosstalk compensation processor 720.
• the combiner 562 is coupled to the subband spatial processor 210 and the crosstalk simulation processor 580, and further coupled to the crosstalk cancellation processor 720.
• the combiner 562 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, and receives the left crosstalk simulation channel WL and a right crosstalk simulation channel WR from the crosstalk simulation processor 580.
• the combiner 562 generates the left enhanced compensation channel TL by combining the left spatially enhanced channel EL and the right crosstalk simulation channel WR, and generates the right enhanced compensation channel TR by combining the right spatially enhanced channel ER and the left crosstalk simulation channel WL.
• the crosstalk compensation processor 720 receives the left enhanced compensation channel TL and the right enhanced compensation channel TR, and performs a crosstalk compensation to generate the left output channel OL and right output channel OR. Additional details regarding the crosstalk compensation processor 720 are discussed below in connection with FIGS. 8 and 9.
• FIG. 8 illustrates an example of a crosstalk compensation processor 800, according to one embodiment.
• the crosstalk compensation processor 800 receives left and right input channels, and generates left and right output channels by applying a crosstalk compensation on the input channels.
• the crosstalk compensation processor 800 is an example of the crosstalk compensation 220 shown in FIG. 2A, the crosstalk compensation processor 420 shown in FIG. 4, the crosstalk compensation processor 520 shown in FIGS.
• the crosstalk compensation processer 800 includes an L/R to M/S converter 812, a mid component processor 820, a side component processor 830, and an M/S to L/R converter 814.
• the crosstalk compensation processor 800 receives left and right input channels (e.g., XL and XR), and performs a crosstalk compensation processing, such as to generate the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR.
• the channels ZL, ZR may be used to compensate for any artifacts in crosstalk processing, such as crosstalk cancellation or simulation.
• the L/R to M/S converter 812 receives the left input audio channel XL and the right input audio channel XR, and generates the nonspatial component X m and the spatial component X s of the input channels XL, XR.
• the left and right channels may be summed to generate the nonspatial component of the left and right channels, and subtracted to generate the spatial component of the left and right channels.
• the mid component processor 820 includes a plurality of filters 840, such as m mid filters 840(a), 840(b), through 840(m).
• each of the m mid filters 840 processes one of m frequency bands of the nonspatial component X m .
• the mid component processor 820 generates a mid crosstalk compensation channel Z m by processing the nonspatial component Xm.
• the mid filters 840 are configured using a frequency response plot of the nonspatial Xm with crosstalk processing through simulation.
• any spectral defects such as peaks or troughs in the frequency response plot over a predetermined threshold (e.g., 10 dB) occurring as an artifact of the crosstalk processing can be estimated.
• a predetermined threshold e.g. 10 dB
• These artifacts result primarily from the summation of the delayed and possibly inverted (e.g., for crosstalk cancellation) contralateral signals with their corresponding ipsilateral signal in the crosstalk processing, thereby effectively introducing a comb filter-like frequency response to the final rendered result.
• the mid crosstalk compensation channel Z m can be generated by the mid component processor 820 to compensate for the estimated peaks or troughs, where each of the m frequency bands corresponds with a peak or trough.
• Each of the mid filters 840 may be configured to adjust for one or more of the peaks and troughs.
• the side component processor 830 includes a plurality of filters 850, such as m side filters 850(a), 850(b) through 850(m).
• the side component processor 830 generates a side crosstalk compensation channel Z s by processing the spatial component X s.
• a frequency response plot of the spatial X s with crosstalk processing can be obtained through simulation.
• any spectral defects such as peaks or troughs in the frequency response plot over a predetermined threshold (e.g., 10 dB) occurring as an artifact of the crosstalk processing can be estimated.
• the side crosstalk compensation channel Z s can be generated by the side component processor 830 to compensate for the estimated peaks or troughs.
• Each of the side filters 850 may be configured to adjust for one or more of the peaks and troughs.
• the mid component processor 820 and the side component processor 830 may include a different number of filters.
• the mid filters 840 and side filters 850 may include a biquad filter having a transfer function defined by Equation 1 :
• X is the input vector
• Y is the ouput.
• Other topologies may be used, depending on their maximum word-length and saturation behaviors.
• the biquad can then be used to implement a second-order filter with real- valued inputs and outputs.
• a discrete-time filter a continuous-time filter is designed, and then transformed into discrete time via a bilinear transform. Furthermore, resulting shifts in center frequency and bandwidth may be compensated using frequency warping.
• a peaking filter may have an S-plane transfer function defined by Equation 3 :
• ⁇ 3 ⁇ 4 — 2cos(u> 0 )
• the filter quality Q may be defined by Equation 4:
• D/ is a bandwidth and f c is a center frequency.
• the M/S to L/R converter 814 receives the mid crosstalk compensation channel Z m and the side crosstalk compensation channel Z s , and generates the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR.
• the mid and side channels may be summed to generate the left channel of the mid and side components, and the mid and side channels may be subtracted to generate right channel of the mid and side components.
• the crosstalk compensation processor 800 receives the left crosstalk simulation channel WL and the right crosstalk simulation channel WR from the crosstalk simulation processor 580, and performs a preprocessing (e.g., as discussed above for the input channels XL and XR) to generate left simulation compensation channel SCL and the right simulation compensation channel SCR.
• a preprocessing e.g., as discussed above for the input channels XL and XR
• the crosstalk compensation processor 800 receives the left enhanced compensation channel TL and the right enhanced compensation channel TR from the combiner 562, and performs a preprocessing (e.g., as discussed above for the input channels XL and XR) to generate left output channel OL and the right output channel OR.
• a preprocessing e.g., as discussed above for the input channels XL and XR
• FIG. 9 illustrates an example of a crosstalk compensation processor 900, according to one embodiment. ETnlike the crosstalk compensation processor 800, the crosstalk compensation processor 900 performs processing on the nonspatial component X m , rather than both the nonspatial component X m and the spatial component X s.
• the crosstalk compensation processor 900 is another example of the crosstalk compensation 220 shown in FIG. 2A, the crosstalk compensation processor 420 shown in FIG. 4, the crosstalk compensation processor 520 shown in FIGS. 5A, 5B, and 5C, or the crosstalk compensation processor 720 shown in FIG. 7.
• the crosstalk compensation processor 900 includes an L&R combiner 910, the mid component processor 820, and an M to L/R converter 960.
• crosstalk compensation processor 900 When the crosstalk compensation processor 900 is part of the audio system
• the L&R combiner 910 receives the left input audio channel XL and the right input audio channel XR, and generates the nonspatial component X m by adding the channels XL, XR.
• the mid component processor 820 receives the nonspatial component X m , and generates the mid crosstalk compensation channel Z m by processing the nonspatial component X m using the mid filters 840(a) through 840(m).
• the M to L/R converter 950 receives the mid crosstalk compensation channel Z m , generates each of left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR using the mid crosstalk compensation channel Z m.
• the crosstalk compensation processor 900 is part of the audio system 400 , 502, or 700, for example, the input and output signals may be different as discussed above for the crosstalk compensation processor 800.
• FIG. 10 illustrates an example of a crosstalk compensation processor 222, according to one embodiment.
• the crosstalk compensation processor 222 is a component of the audio system 202 as discussed above in connection with FIG. 2B.
• the crosstalk compensation processor 222 outputs the mid crosstalk compensation channel Z m.
• the crosstalk compensation process 900 includes the L&R combiner 910 and the mid component processor 820, as discussed above for the crosstalk compensation processor 900.
• FIG. 11 illustrates an example of a crosstalk compensation processor 1100, according to one embodiment.
• the crosstalk compensation processor 1100 is an example of the crosstalk compensation processor 320 shown in FIG. 3, or the crosstalk compensation processor 620 shown in FIG. 6.
• the crosstalk compensation processor 1100 is integrated within the subband spatial processor.
• the crosstalk compensation processor 1100 receives input mid E m and side E s components of a signal, and performs crosstalk compensation on the mid and side components to generate mid Tm and side T s output channels.
• the crosstalk compensation processor 1100 includes the mid component processor 820 and the side component processor 830.
• the mid component processor 820 receives the enhanced nonspatial component E m from the spatial frequency band processor 245, and generates the mid enhanced compensation channel T m using the mid filters 840(a) through 840(m).
• the side component processor 830 receives the enhanced spatial component E s from the spatial frequency band processor 245, and generates the side enhanced compensation channel T s using the side filters 850(a) through 850(m).
• FIG. 12 illustrates an example of a spatial frequency band divider 240, according to one embodiment.
• the spatial frequency band divider 240 is a component of the subband spatial processor 210, 310, or 610 shown in FIGS. 2A through 7.
• the spatial frequency band divider 240 includes an L/R to M/S converter 1212 that receives the left input channel XL and the right input channel XR, and converts these inputs into the spatial component Y m and the nonspatial component Y s.
• FIG. 13 illustrates an example of a spatial frequency band processor 245, according to one embodiment.
• the spatial frequency band processor 245 is a component of the subband spatial processor 210, 310, or 610 shown in FIGS. 2A through 7.
• the spatial frequency band processor 245 receives the nonspatial component Y m and applies a set of subband filters to generate the enhanced nonspatial subband component E m.
• the spatial frequency band processor 245 also receives the spatial subband component Y s and applies a set of subband filters to generate the enhanced nonspatial subband component E m.
• the subband filters can include various combinations of peak filters, notch filters, low pass filters, high pass filters, low shelf filters, high shelf filters, bandpass filters, bandstop filters, and/or all pass filters.
• the spatial frequency band processor 245 includes a subband filter for each of n frequency subbands of the nonspatial component Y m and a subband filter for each of the n subbands of the spatial component Y s.
• the spatial frequency band processor 245 includes a series of subband filters for the nonspatial component Y m including a mid equalization (EQ) filter 1362(1) for the subband (1), a mid EQ filter 1362(2) for the subband (2), a mid EQ filter 1362(3) for the subband (3), and a mid EQ filter 1362(4) for the subband (4).
• EQ mid equalization
• Each mid EQ filter 1362 applies a filter to a frequency subband portion of the nonspatial component Y m to generate the enhanced nonspatial component E m.
• the spatial frequency band processor 245 further includes a series of subband filters for the frequency subbands of the spatial component Y s , including a side equalization (EQ) filter 1364(1) for the subband (1), a side EQ filter 1364(2) for the subband (2), a side EQ filter 1364(3) for the subband (3), and a side EQ filter 1364(4) for the subband (4).
• Each side EQ filter 1364 applies a filter to a frequency subband portion of the spatial component Y s to generate the enhanced spatial component E s.
• Each of the n frequency subbands of the nonspatial component Y m and the spatial component Y s may correspond with a range of frequencies.
• the frequency subband (1) may corresponding to 0 to 300 Hz
• the frequency subband(2) may correspond to 300 to 510 Hz
• the frequency subband(3) may correspond to 510 to 2700 Hz
• the frequency subband(4) may correspond to 2700 Hz to Nyquist frequency.
• the n frequency subbands are a consolidated set of critical bands.
• the critical bands may be determined using a corpus of audio samples from a wide variety of musical genres. A long term average energy ratio of mid to side components over the 24 Bark scale critical bands is determined from the samples. Contiguous frequency bands with similar long term average ratios are then grouped together to form the set of critical bands.
• the range of the frequency subbands, as well as the number of frequency subbands, may be adjustable.
• FIG. 14 illustrates an example of a spatial frequency band combiner 250, according to one embodiment.
• the spatial frequency band combiner 250 is a component of the subband spatial processor 210, 310, or 610 shown in FIGS. 2A through 7.
• the spatial frequency band combiner 250 receives mid and side components, applies gains to each of the components, and converts the mid and side components into left and right channels.
• the spatial frequency band combiner 250 receives the enhanced nonspatial component E m and the enhanced spatial component E s , and performs global mid and side gains before converting the enhanced nonspatial component E m and the enhanced spatial component E s into the left spatially enhanced channel EL and the right spatially enhanced channel ER.
• the spatial frequency band combiner 250 includes a global mid gain 1422, a global side gain 1424, and an M/S to L/R converter 1426 coupled to the global mid gain 1422 and the global side gain 1424.
• the global mid gain 1422 receives the enhanced nonspatial component E m and applies a gain
• the global side gain 1424 receives the enhanced nonspatial component E s and applies a gain.
• the M/S to L/R converter 1426 receives the enhanced nonspatial component E m from the global mid gain 1422 and the enhanced spatial component E s from the global side gain 1424, and converts these inputs into the left spatially enhanced channel EL and the right spatially enhanced channel ER.
• the spatial frequency band combiner 250 When the spatial frequency band combiner 250 is part of the subband spatial processor 310 shown in FIG. 3 or the subband spatial processor 610 shown in FIG. 6, the spatial frequency band combiner 250 receives the mid enhanced compensation channel Tm instead of the nonspatial component Em, and receives the side enhanced compensation channel T s instead of the nonspatial component E m. The spatial frequency band combiner 250 processes the mid enhanced compensation channel Tm and the side enhanced
• FIG. 15 illustrates a crosstalk cancellation processor 270, according to one embodiment.
• the crosstalk cancellation processor 270 receives the left enhanced compensation channel TL and the right enhanced
• the crosstalk cancellation processor 270 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER, and performs crosstalk cancellation on the channels EL, ER to generate the left enhanced in-out-band crosstalk channel CL and a right enhanced in-out-band crosstalk channel CR.
• the crosstalk cancellation processor 260 includes an in-out band divider 1510, inverters 1520 and 1522, contralateral estimators 1530 and 1540, combiners 1550 and 1552, and an in-out band combiner 1560. These components operate together to divide the input channels TL, TR into in-band components and out-of-band components, and perform a crosstalk cancellation on the in-band components to generate the output channels OL, OR.
• crosstalk cancellation can be performed for a particular frequency band while obviating degradations in other frequency bands. If crosstalk cancellation is performed without dividing the input audio signal T into different frequency bands, the audio signal after such crosstalk cancellation may exhibit significant attenuation or amplification in the nonspatial and spatial components in low frequency (e.g., below 350 Hz), higher frequency (e.g., above 12000 Hz), or both.
• the in- band e.g., between 250 Hz and 14000 Hz
• a balanced overall energy, particularly in the nonspatial component, across the spectrum in the mix can be retained.
• the in-out band divider 1510 separates the input channels TL, TR into in-band channels TL,in, TR,in and out of band channels TL.O I U, TR,out, respectively. Particularly, the in- out band divider 1510 divides the left enhanced compensation channel TL into a left in-band channel TL,in and a left out-of-band channel TL,Out. Similarly, the in-out band divider 1510 separates the right enhanced compensation channel TR into a right in-band channel TR,in and a right out-of-band channel TR,out.
• Each in-band channel may encompass a portion of a respective input channel corresponding to a frequency range including, for example, 250 Hz to 14 kHz. The range of frequency bands may be adjustable, for example according to speaker parameters.
• the inverter 1520 and the contralateral estimator 1530 operate together to generate a left contralateral cancellation component SL to compensate for a contralateral sound component due to the left in-band channel TL,in.
• the inverter 1522 and the contralateral estimator 1540 operate together to generate a right contralateral cancellation component SR to compensate for a contralateral sound component due to the right in-band channel TR,in.
• the inverter 1520 receives the in-band channel TL,in and inverts a polarity of the received in-band channel TL,in to generate an inverted in-band channel TL,in ⁇
• the contralateral estimator 1530 receives the inverted in-band channel TL,in’, and extracts a portion of the inverted in-band channel TL,in’ corresponding to a contralateral sound component through filtering. Because the filtering is performed on the inverted in- band channel TL,in’, the portion extracted by the contralateral estimator 1530 becomes an inverse of a portion of the in-band channel TL,in attributing to the contralateral sound component.
• the portion extracted by the contralateral estimator 1530 becomes a left contralateral cancellation component SL, which can be added to a counterpart in-band channel TR,in to reduce the contralateral sound component due to the in-band channel TL,in.
• the inverter 1520 and the contralateral estimator 1530 are implemented in a different sequence.
• the inverter 1522 and the contralateral estimator 1540 perform similar operations with respect to the in-band channel TR,in to generate the right contralateral cancellation component SR. Therefore, detailed description thereof is omitted herein for the sake of brevity.
• the contralateral estimator 1530 includes a filter 1532, an amplifier 1534, and a delay unit 1536.
• the filter 1532 receives the inverted input channel TL,in’ and extracts a portion of the inverted in-band channel TL,in’
• G CIB Gain in decibels
• G dB -3.0 - logi .333 (D) Eq. (5)
• D is a delay amount by delay unit 1536 and 1546 in samples, for example, at a sampling rate of 48 KHz.
• An alternate implementation is a Lowpass filter with a corner frequency selected between 5000 and 10000 Hz, and Q selected between 0.5 and 1.0.
• the contralateral estimator 1540 includes a filter 1542, an amplifier 1544, and a delay unit 1546 that performs similar operations on the inverted in-band channel TR,i n ’ to generate the right contralateral cancellation component SR.
• the contralateral estimators 1530, 1540 generate the left and right contralateral cancellation components SL, SR, according to equations below:
• the configurations of the crosstalk cancellation can be determined by the speaker parameters.
• filter center frequency, delay amount, amplifier gain, and filter gain can be determined, according to an angle formed between two speakers 280 with respect to a listener.
• values between the speaker angles are used to interpolate other values.
• the combiner 1550 combines the right contralateral cancellation component SR to the left in-band channel TL,in to generate a left in-band crosstalk channel UL, and the combiner 1552 combines the left contralateral cancellation component SL to the right in-band channel TR,in to generate a right in-band crosstalk channel UR.
• the in-out band combiner 1560 combines the left in-band crosstalk channel UL with the out-of-band channel TL,Out to generate the left output channel OL, and combines the right in-band crosstalk channel UR with the out-of-band channel TR,out to generate the right output channel OR.
• the left output channel OL includes the right contralateral cancellation component SR corresponding to an inverse of a portion of the in-band channel TR,III attributing to the contralateral sound
• the right output channel OR includes the left contralateral cancellation component SL corresponding to an inverse of a portion of the in- band channel TL,in attributing to the contralateral sound.
• a wavefront of an ipsilateral sound component output by the loudspeaker 280R according to the right output channel OR arrived at the right ear can cancel a wavefront of a contralateral sound component output by the loudspeaker 280L according to the left output channel OL.
• a wavefront of an ipsilateral sound component output by the speaker 280L according to the left output channel OL arrived at the left ear can cancel a wavefront of a contralateral sound component output by the loudspeaker 280R according to right output channel OR.
• contralateral sound components can be reduced to enhance spatial detectability.
• FIG. 16A illustrates a crosstalk simulation processor 1600, according to one embodiment.
• the crosstalk simulation processor 1600 is an example of the crosstalk simulation processor 580 of the audio systems 500, 502, 504, 600, and 700 as shown in FIGS. 5 A, 5B, 5C, 6, and 7, respectively.
• the crosstalk simulation processor 1600 generates contralateral sound components for output to the head-mounted speakers 580L and 580R, thereby providing a loudspeaker-like listening experience on the head-mounted speakers 580L and 580R.
• the crosstalk simulation processor 1600 includes a left head shadow low-pass filter 1602, a left cross-talk delay 1604, and a left head shadow gain 1610 to process the left input channel XL.
• the crosstalk simulation processor 1600 further includes a right head shadow low-pass filter 1606, a right cross-talk delay 1608, and a right head shadow gain 1612 to process the right input channel XR.
• the left head shadow low-pass filter 1602 receives the left input channel XL and applies a modulation that models the frequency response of the signal after passing through the listener’s head.
• the output of the left head shadow low-pass filter 1602 is provided to the left cross-talk delay 1604, which applies a time delay to the output of the left head shadow low-pass filter 1602.
• the time delay represents trans-aural distance that is traversed by a contralateral sound component relative to an ipsilateral sound component.
• the frequency response can be generated based on empirical experiments to determine frequency dependent characteristics of sound wave modulation by the listener’s head. For example and with reference to FIG.
• the contralateral sound component 112L that propagates to the right ear 125R can be derived from the ipsilateral sound component 118L that propagates to the left ear 125L by filtering the ipsilateral sound component 118L with a frequency response that represents sound wave modulation from trans-aural propagation, and a time delay that models the increased distance the contralateral sound component 112L travels (relative to the ipsilateral sound component 118R) to reach the right ear 125R.
• the cross-talk delay 1604 is applied prior to the head shadow low-pass filter 1602.
• the left head shadow gain 1610 applies a gain to the output of the left crosstalk crosstalk delay 1604 to generate the left crosstalk simulation channel WL.
• the application of the head shadow low-pass filter, crosstalk delay, and head shadow gain for each of the left and right channels may be performed in different orders.
• the right head shadow low-pass filter 1606 receives the right input channel XR and applies a modulation that models the frequency response of the listener’s head.
• the output of the right head shadow low-pass filter 1606 is provided to the right crosstalk delay 1608, which applies a time delay to the output of the right head shadow low-pass filter 1606.
• the right head shadow gain 1612 applies a gain to the output of the right crosstalk delay 1608 to generate the right crosstalk simulation channel WR.
• the head shadow low-pass filters 1602 and 1606 have a cutoff frequency of 2,023 Hz.
• the cross-talk delays 1604 and 1608 apply a 0.792
• FIG. 16B illustrates a crosstalk simulation processor 1650, according to one embodiment.
• the crosstalk simulation processor 1650 is another example of the crosstalk simulation processor 580 of the audio systems 500, 502, 504, 600, and 700 as shown in FIGS. 5A, 5B, 5C, 6, and 7, respectively.
• the crosstalk simulation processor 1650 further includes a left head shadow high-pass filter 1624 and a right head shadow high-pass filter 1626.
• the left head shadow high-pass filter 1624 applies a modulation to the left input channel XL that models the frequency response of the signal after passing through the listener’s head
• the right head shadow high-pass filter applies a modulation to the right input channel XR that models the frequency response of the signal after passing through the listener’s head.
• the use of both low-pass and high-pass filters on the left and right input channels XL and XR may result in a more accurate model of the frequency response though the listener’s head.
• the components of the crosstalk simulation processors 1600 and 1650 may be arranged in different orders.
• crosstalk simulation processor 1650 includes the left head shadow low-pass filter 1602 coupled with the left head shadow high- pass filter 1625, the left head shadow high-pass filter 1625 coupled to the left crosstalk delay 1604, and the left crosstalk delay 1640 coupled to the left head shadow gain 1610
• the components 1602, 1624, 1604, and 1610 may be rearranged to process the left input channel XL in different orders.
• the components 1606, 1626, 1608, and 1612 that process the right input channel XR may be arranged in different orders.
• FIG. 17 illustrates a combiner 260, according to one embodiment.
• the combiner 260 may be part of the audio system 200 shown in FIG. 2A.
• the combiner 260 includes a sum left 1702, a sum right 1704, and an output gain 1706.
• the sum left 1702 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, and receives the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR from the crosstalk compensation processor 220.
• the sum left 1702 combines the left spatially enhanced channel EL with left crosstalk compensation channel ZL to generate the left enhanced compensation channel TL.
• the sum right 1704 combines the right spatially enhanced channel ER with the right crosstalk compensation channel ZR to generate the right enhanced compensation channel TR.
• the output gain 1706 applies a gain to the left enhanced compensation channel TL, and outputs the left enhanced compensation channel TL.
• the output gain 1706 also applies a gain to the right enhanced compensation channel TR, and outputs the right enhanced compensation channel TR.
• FIG. 18 illustrates a combiner 262, according to one embodiment.
• the combiner 262 may be part of the audio system 202 shown in FIG. 2B.
• the combiner 262 includes the sum left 1702, the sum right 1704, and the output gain 1706 as discussed above for the combiner 260.
• the combiner 262 receives the mid crosstalk compensation signal Zmfrom the crosstalk compensation processor 222.
• the M to L/R converter 1826 that separates the mid crosstalk compensation signal Z m into a left crosstalk compensation channel ZL and a right crosstalk compensation channel ZR.
• the sum left 1702 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, and receives the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR from the M to L/R converter 1826.
• the sum left 1702 combines the left spatially enhanced channel EL with left crosstalk
• the sum right 1704 combines the right spatially enhanced channel ER with the right crosstalk compensation channel ZR to generate the right enhanced compensation channel TR.
• the output gain 1706 applies a gain to the left enhanced compensation channel TL, and outputs the left enhanced compensation channel TL.
• the output gain 1706 also applies a gain to the right enhanced compensation channel TR, and outputs the right enhanced compensation channel TR.
• FIG. 19 illustrates a combiner 560, according to one embodiment.
• the combiner 560 may be part of the audio system 500 shown in FIG. 5 A.
• the combiner 560 includes a sum left 1902, a sum right 1904, and an output gain 1906.
• the sum left 1902 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, receives the left crosstalk compensation channel ZL and the right crosstalk compensation channel ZR from the crosstalk compensation processor 520, and receives the left crosstalk simulation channel WL and the right crosstalk simulation channel WR from the crosstalk simulation processor 580.
• the sum left 1902 combines the left spatially enhanced channel EL, the left crosstalk compensation channel ZL, and the right crosstalk simulation channel WR to generate the left output channel OL.
• the sum right 1904 combines the right spatially enhanced channel ER, the right crosstalk compensation channel ZR, and the left crosstalk simulation channel WL to generate the right output channel OR.
• the output gain 1906 applies a gain to the left output channel OL, and outputs the left output channel OL.
• the output gain 1906 also applies a gain to the right output channel OR, and outputs the right output channel OR.
• FIG. 20 illustrates a combiner 562, according to one embodiment.
• the combiner 562 may be part of the audio system 502, 504, 600, and 700 shown in FIGS. 5B,
• the combiner 562 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, receives the left simulation compensation channel SCL and the right simulation compensation channel SCR, and generates the left output channel OL and the right output channel OR.
• the sum left 2002 combines the left spatially enhanced channel EL and the left simulation compensation channel SCL to generate the left output channel OL.
• the sum right 2004 combines the right spatially enhanced channel ER and the right simulation compensation channel SCR to generate the right output channel OR.
• the output gain 2006 applies gains to the left output channel OL and the right output channel OR, and outputs the left output channel OL and the right output channel OR.
• the combiner 562 receives the left enhanced compensation channel TL and the right enhanced compensation channel TR from the subband spatial processor 610, receives the left crosstalk simulation channel WL and the right crosstalk simulation channel WR from the crosstalk simulation processor 580.
• the sum left 2002 generates the left output channel OL by combining the left enhanced compensation channel TL and the right crosstalk simulation channel WR.
• the sum right 2004 generates the right output channel OR by combining the right enhanced compensation channel TR and the left crosstalk simulation channel WL.
• the combiner 562 receives the left spatially enhanced channel EL and the right spatially enhanced channel ER from the subband spatial processor 210, and receives the left crosstalk simulation channel WL and the right crosstalk simulation channel WR from the crosstalk simulation processor 580.
• the sum left 2002 generates the left enhanced compensation channel TL by combining the left spatially enhanced channel EL and the right crosstalk simulation channel WR.
• the sum right 2004 generates the right enhanced compensation channel TR by combining the right spatially enhanced channel ER and the left crosstalk simulation channel WL.
• a crosstalk compensation processor may compensate for comb-filtering artifacts that occur in the spatial and nonspatial signal components as a result of various crosstalk delays and gains in crosstalk cancellation. These crosstalk cancellation artifacts may be handled by applying correction filters to the non-spatial and spatial components independently. Mid/Side filtering (with associated M/S de-matrixing) can be inserted at various points in the overall signal flow of the algorithms, and the crosstalk- induced comb-filter peaks and notches in the frequency response of the spatial and nonspatial signal components may be handled in parallel.
• FIGS. 21-26 illustrate effects on the spatial and nonspatial signal components when applying the filters of a crosstalk compensation processor for different speaker angle and speaker size configurations, with only crosstalk cancellation processing applied to an input signal.
• the crosstalk compensation processor can selectively flatten the frequency response of the signal components, providing a minimally colored and minimally gain- adjusted post-crosstalk-cancelled output.
• compensation filters are applied to the spatial and nonspatial components independently, targeting all comb-filter peaks and/or troughs in the nonspatial (L+R, or mid) component, and all but the lowest comb-filter peaks and/or troughs in the spatial (L-R, or side) component.
• the method of compensation can be procedurally derived, tuned by ear and hand, or a combination.
• FIG. 21 illustrates a plot 2100 of a crosstalk cancelled signal, according to one embodiment.
• the line 2102 is a white noise input signal.
• the line 2104 is a nonspatial component of the input signal with crosstalk cancellation.
• the line 2106 is a spatial component of the input signal with crosstalk cancellation.
• the crosstalk cancellation may include a crosstalk delay of 1 sample @48 KHz sampling rate, a crosstalk gain of -3 dB, and an in-band frequency range defined by a low frequeny bypass of 350 Hz and a high frequency bypass of 12000 Hz.
• FIG. 22 illustrates a plot 2200 for crosstalk compensation applied to the nonspatial component of FIG. 21, according to one embodiment.
• the line 2204 represents the crosstalk compensation applied to the nonspatial component of the input signal with crosstalk cancellation, as represented by the line 2104 in FIG. 21.
• two mid filters are applied to the crosstalk cancelled nonspatial component including a peaknotch filter having a 1000 Hz center frequency, a 12.5 dB gain, and 0.4 Q, and another peaknotch filter having a 15000 Hz center frequency, a -1 dB gain, and 1.0 Q.
• the line 2106 representing the spatial component of the input signal with crosstalk cancellation may also be modified with a crosstalk compensation.
• FIG. 23 illustrates a plot 2300 of a crosstalk cancelled signal, according to one embodiment.
• the line 2302 is a white noise input signal.
• the line 2304 is a nonspatial component of the input signal with crosstalk cancellation.
• the line 2306 is a spatial component of the input signal with crosstalk cancellation.
• the crosstalk cancellation may include a crosstalk delay of 3 samples @48 KHz sampling rate, a crosstalk gain of -6.875 dB, and an in-band frequency range defined by a low frequeny bypass of 350 Hz and a high frequency bypass of 12000 Hz.
• FIG. 24 illustrates a plot 2400 for crosstalk compensation applied to the nonspatial component and spatial component of FIG. 23, according to one embodiment.
• the line 2404 represents the crosstalk compensation applied to the nonspatial component of the input signal with crosstalk cancellation, as represented by the line 2304 in FIG. 23.
• Three mid filters are applied to the crosstalk cancelled nonspatial component including a first peaknotch filter having a 650 Hz center frequency, an 8.0 dB gain, and 0.65 Q, a second peaknotch filter having a 5000 Hz center frequency, a -3.5 dB gain, and 0.5 Q, and a third peaknotch filter having a 16000 Hz center frequency, a 2.5 dB gain, and 2.0 Q.
• the line 2406 represents the crosstalk compensation applied to the spatial component of the input signal with crosstalk cancellation, as represented by the line 2306 in FIG. 23.
• Two side filters are applied to the crosstalk cancelled spatial component including a first peaknotch filter having a 6830 Hz center frequency, an 4.0 dB gain, and 1.0 Q, and a second peaknotch filter having a 15500 Hz center frequency, a -2.5 dB gain, and 2.0 Q.
• the number of mid and side filters applied by the crosstalk compensation processor, as well as their parameters, may vary.
• FIG. 25 illustrates a plot 2500 of a crosstalk cancelled signal, according to one embodiment.
• the line 2502 is a white noise input signal.
• the line 2504 is a nonspatial component of the input signal with crosstalk cancellation.
• the line 2506 is a spatial component of the input signal with crosstalk cancellation.
• the crosstalk cancellation may include a crosstalk delay of 5 samples @48 KHz sampling rate, a crosstalk gain of -8.625 dB, and an in-band defined by a low frequeny bypass of 350 Hz and a high frequency bypass of 12000 Hz.
• FIG. 26 illustrates a plot 2600 for crosstalk compensation applied to the nonspatial component and spatial component of FIG. 25, according to one embodiment.
• the line 2604 represents the crosstalk compensation applied to the nonspatial component of the input signal with crosstalk cancellation, as represented by the line 2504 in FIG. 25.
• the line 2606 represents the crosstalk compensation applied to the spatial component of the input signal with crosstalk cancellation, as represented by the line 2506 in FIG. 25.
• Three side filters are applied to the crosstalk cancelled spatial component including a first peaknotch filter having a 4000 Hz center frequency, an 8.0 dB gain, and 2.0 Q, and second peaknotch filter having an 8800 Hz center frequency, a -2.0 dB gain, and 1.0 Q, and a third peaknotch filter having a 15000 Hz center frequency, a 1.5 dB gain, and 2.5 Q.
• FIG. 27A illustrates a table 2700 of filter settings for a crosstalk compensation processor as a function of crosstalk cancellation delays, according to one embodiment.
• the table 2700 provides center frequency (Fc), gain, and Q values for a mid filter 840 of a crosstalk compensation processor when the crosstalk cancellation processor applies an in-band frequency range of 350 to 12000 Hz @48 KHz.
• FIG. 27B illustrates a table 2750 of filter settings for a crosstalk compensation processor as a function of crosstalk cancellation delays, according to one embodiment.
• the table 2750 provides center frequency (Fc), gain, and Q values for a mid filter 840 of a crosstalk compensation processor when the crosstalk cancellation processor applies an in-band frequency range of 200 to 14000 Hz @48 KHz.
• different crosstalk delay times may be caused by speaker positions or angles, for example, and may result in different comb-filtering artifacts.
• different in-band frequencies used in crosstalk cancellation may also result in different comb-filtering artifacts.
• the mid and side filters of the crosstalk cancellation processor may apply different settings for the center frequency, gain, and Q to compensate for the comb-filtering artifacts.
• the audio systems discussed herein perform various types of processing on an input audio signal including subband spatial processing (SBS), crosstalk compensation processing (CCP), and crosstalk processing (CP).
• the crosstalk processing may include crosstalk simulation or crosstalk cancellation.
• the order of processing for SBS, CCP, and CP may vary.
• various steps of the SBS, CCP, or CP processing may be integrated.
• FIGS. 28 A, 28B, 28C, 28D, and 28E Some examples of processing embodiments are shown in FIGS. 28 A, 28B, 28C, 28D, and 28E for when the crosstalk processing is crosstalk cancellation, and in FIGS. 29A, 29B, 29C, 29D, 29E, 29F, 29G, and 29H for when the crosstalk processing is crosstalk simulation.
• subband spatial processing is performed in parallel with crosstalk compensation processing on the input audio signal X to generate a result, then crosstalk cancellation processing is applied to the result to generate the output audio signal O.
• the subband spatial processing is integrated with the crosstalk compensation processing to generate a result from the input audio signal X.
• An example is shown in FIG. 3 where the crosstalk compensation processor 320 is integrated with the subband spatial processor 310.
• Crosstalk cancellation processing is then applied to the result to generate the output audio signal O.
• the subband spatial processing is performed on the input audio signal X to generate a result
• crosstalk cancellation processing is performed on the result of the subband spatial processing
• crosstalk compensation processing is performed on the result of the crosstalk cancellation processing to generate the output audio signal O.
• the crosstalk compensation processing is performed on the input audio signal X to generate a result
• subband spatial processing is performed on the result of the crosstalk compensation processing
• crosstalk cancellation processing is performed on the result of the crosstalk compensation processing to generate the output audio signal O.
• subband spatial processing is performed on the input audio signal X to generate a result
• crosstalk compensation processing is performed on the result of the subband spatial processing
• crosstalk cancellation processing is performed on the result of the crosstalk compensation processing to generate the output audio signal O.
• subband spatial processing is performed on the input audio signal X in parallel with crosstalk simulation processing and crosstalk compensation processing being performed on the input audio signal X.
• the parallel results are combined to generate the output audio signal O.
• the crosstalk simulation processing is applied before the crosstalk compensation processing.
• subband spatial processing is performed on the input audio signal X in parallel with crosstalk compensation processing and crosstalk simulation processing being performed on the input audio signal X.
• the parallel results are combined to generate the output audio signal O.
• the crosstalk compensation processing is applied before the crosstalk simulation processing.
• subband spatial processing is integrated with crosstalk compensation processing to generate a result from the input audio signal X.
• crosstalk simulation processing is applied to the input audio signal X.
• the parallel results are combined to generate the output audio signal O.
• subband spatial processing and crosstalk simulation processing are each applied to the input audio signal X.
• Crosstalk compensation processing is applied to the parallel results to generate the output audio signal O.
• crosstalk simulation processing is applied to the input audio signal X in parallel with crosstalk compensation processing and subband spatial processing being applied to the input signal X.
• the parallel results are combined to generate the output audio signal O.
• the crosstalk compensation processing is performed before the subband spatial processing.
• crosstalk simulation processing is applied to the input audio signal X in parallel with subband spatial processing and crosstalk compensation processing being applied to the input signal X.
• the parallel results are combined to generate the output audio signal O.
• the subband spatial processing is performed before the crosstalk compensation processing.
• crosstalk compensation processing is applied to the input audio signal.
• Subband spatial processing and crosstalk simulation are applied in parallel to the result of the crosstalk compensation processing.
• the result of the subband spatial processing and crosstalk simulation processing are combined to generate the output audio signal O.
• FIG. 30 is a schematic block diagram of a computer 3000, according to one embodiment.
• the computer 3000 is an example of circuitry that implements an audio system. Illustrated are at least one processor 3002 coupled to a chipset 3004.
• the chipset 3004 includes a memory controller hub 3020 and an input/output (I/O) controller hub 3022.
• a memory 3006 and a graphics adapter 3012 are coupled to the memory controller hub 3020, and a display device 3018 is coupled to the graphics adapter 3012.
• a storage device 3008, keyboard 3010, pointing device 3014, and network adapter 3016 are coupled to the I/O controller hub 3022.
• the computer 3000 may include various types of input or output devices. Other embodiments of the computer 3000 have different architectures.
• the memory 3006 is directly coupled to the processor 3002 in some embodiments.
• the storage device 3008 includes one or more non-transitory computer- readable storage media such as a hard drive, compact disk read-only memory (CD-ROM), DVD, or a solid-state memory device.
• the memory 3006 holds instructions and data used by the processor 3002.
• the pointing device 3014 is used in combination with the keyboard 3010 to input data into the computer system 3000.
• the graphics adapter 3012 displays images and other information on the display device 3018. In some embodiments, the display device 3018 includes a touch screen capability for receiving user input and selections.
• the network adapter 3016 couples the computer system 3000 to a network. Some embodiments of the computer 3000 have different and/or other components than those shown in FIG. 30.
• the computer 3000 is adapted to execute computer program modules for providing functionality described herein.
• some embodiments may include a computing device including one or more modules configured to perform the processing as discussed herein.
• the term“module” refers to computer program instructions and/or other logic used to provide the specified functionality.
• a module can be implemented in hardware, firmware, and/or software.
• program modules formed of executable computer program instructions are stored on the storage device 3008, loaded into the memory 3006, and executed by the processor 3002.
• a software module is implemented with a computer program product comprising a computer readable medium (e.g., non-transitory computer readable medium) containing computer program code, which can be executed by a computer processor for performing any or all of the steps, operations, or processes described.
• a computer readable medium e.g., non-transitory computer readable medium

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